2017 Antarctic OMI and MERRA Ozone
Daily progression and annual means
The daily progression through the 2017 ozone hole season of the various ozone statistics, comparing 2017 to the climatology of all other years. Clicking a link will bring up, in a new window, a PDF vector plot or a plain-text ASCII data file that is suitable for input into any program. The annual plots show the range of daily values that go into each year's average with gray shading.
ozone hole area
The ozone hole area is determined from total ozone satellite measurements. It is defined to be that region of ozone values below 220 Dobson Units (DU) located south of 40°S. Values below 220 DU represent anthropogenic ozone losses over Antarctica. The annual data are for 7 September–13 October, 1979–2016. On the annual plot, the area of North America is also show for reference.
The minimum ozone is found from total ozone satellite measurements south of 40°S. No interpolation of missing values is performed. This means that the actual minimum value on a day may be estimated too high, especially in the polar night region. The annual data are for 21 September–16 October.
ozone mass deficit
ozone mean latitude bands
The monthly-mean ozone for seven latitude bands: 90°S–60°S, 60°S–30°S, 30°S–10°S, 10°S–10°N, 10°S–30°N, 30°S–60°N, 60°S–90°N. No interpolation of missing values is performed. Since the instruments only measure in sunlight, the actual 90°S–60°S values during April through September and the 60°S–90°N values during during October through March may be biased towards the lower latitudes.
The depth and area of the ozone hole are primarily governed by the amounts of chlorine and bromine in the Antarctic stratosphere. Very low temperatures are needed to form polar stratospheric clouds (PSCs). Chlorine gases react on the surface of these PSCs to release chlorine into a form that can easily destroy ozone. The chlorine and bromine chemical catalytic reactions that destroy ozone need sunlight. Hence, the ozone hole begins to grow as the sun is rising over Antarctica at the end of the winter.
The ozone hole begins to grow in August and reaches its largest area in depth from the middle of September to early October. In the early years (before 1984) the hole was small because chlorine and bromine levels over Antarctica were low. Year-to-year variations in area and depth are caused by year-to-year variations in temperature. Colder conditions result in a larger area and lower ozone values in the center of the hole.
The data starting from November 2004 are from the OMI instrument (KNMI / NASA) onboard the Aura satellite. They are the OMTO3d that have been processed in a manner similar to the TOMS data from earlier years.
The ozone minimum is determined only from data actually contained in the processed satellite data. To calculate the ozone hole area and mass deficit, we fill in missing areas (bad orbits and polar night) from an atmospheric model. MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5). The Project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales and places the NASA EOS suite of observations in a climate context. Since these data are from a reanalysis, they are not up-to-date. So, we supplement with the GEOS-5 FP data that are also produced by the GEOS-5 model in near real time.